Method and apparatus for handling timer related to radio link failure in wireless communication system

ABSTRACT

The present disclosure relates to handling a timer related to a radio link failure (RLF) in wireless communications. According to an embodiment of the present disclosure, a method performed by a wireless device in a wireless communication system comprises: receiving a conditional mobility command comprising a mobility execution condition for a target cell; detecting that an entering condition of the mobility execution condition is satisfied while a timer is running, wherein a radio link failure (RLF) is detected upon an expiry of the timer; stopping the timer based on detecting that the entering condition of the mobility execution condition is satisfied; and performing a mobility to the target cell based on that the entering condition is satisfied for at least a time to trigger (TTT) related to the mobility execution condition.

TECHNICAL FIELD

The present disclosure relates to handling a timer related to a radiolink failure (RLF) in wireless communications.

BACKGROUND

3rd generation partnership project (3GPP) long-term evolution (LTE) is atechnology for enabling high-speed packet communications. Many schemeshave been proposed for the LTE objective including those that aim toreduce user and provider costs, improve service quality, and expand andimprove coverage and system capacity. The 3GPP LTE requires reduced costper bit, increased service availability, flexible use of a frequencyband, a simple structure, an open interface, and adequate powerconsumption of a terminal as an upper-level requirement.

Work has started in international telecommunication union (ITU) and 3GPPto develop requirements and specifications for new radio (NR) systems.3GPP has to identify and develop the technology components needed forsuccessfully standardizing the new RAT timely satisfying both the urgentmarket needs, and the more long-term requirements set forth by the ITUradio communication sector (ITU-R) international mobiletelecommunications (IMT)-2020 process. Further, the NR should be able touse any spectrum band ranging at least up to 100 GHz that may be madeavailable for wireless communications even in a more distant future.

The NR targets a single technical framework addressing all usagescenarios, requirements and deployment scenarios including enhancedmobile broadband (eMBB), massive machine-type-communications (mMTC),ultra-reliable and low latency communications (URLLC), etc. The NR shallbe inherently forward compatible.

In wireless communications, due to a degradation of radio link quality,RLF may occur. To handle the RLF, various timers may be adopted, such asT310 timer and T312 timer. These timers may be started if/when asituation in which RLF may occur with relatively high probability, andmay be stopped if/when the situation ends. At an expiry of these timers,RLF may occur. Theses RLF timers should be handled so that the RLF mayoccur in a proper situation.

SUMMARY 1. Technical Problem

An aspect of the present disclosure is to provide method and apparatusfor handling a timer related to RLF in a wireless communication system.

Another aspect of the present disclosure is to provide method andapparatus for handling a timer related to RLF in conditional mobility ina wireless communication system.

Another aspect of the present disclosure is to provide method andapparatus for determining when to start the timer related to RLF inconditional mobility in a wireless communication system.

Another aspect of the present disclosure is to provide method andapparatus for determining when to stop the timer related to RLF inconditional mobility in a wireless communication system.

2. Technical Solution

According to an embodiment of the present disclosure, a method performedby a wireless device in a wireless communication system comprises:receiving a conditional mobility command comprising a mobility executioncondition for a target cell; detecting that an entering condition of themobility execution condition is satisfied while a timer is running,wherein a radio link failure (RLF) is detected upon an expiry of thetimer; stopping the timer based on detecting that the entering conditionof the mobility execution condition is satisfied; and performing amobility to the target cell based on that the entering condition issatisfied for at least a time to trigger (TTT) related to the mobilityexecution condition.

According to an embodiment of the present disclosure, a wireless devicein a wireless communication system comprises: a transceiver; a memory;and at least one processor operatively coupled to the transceiver andthe memory, and configured to: control the transceiver to receive aconditional mobility command comprising a mobility execution conditionfor a target cell; detect that an entering condition of the mobilityexecution condition is satisfied while a timer is running, wherein aradio link failure (RLF) is detected upon an expiry of the timer; stopthe timer based on detecting that the entering condition of the mobilityexecution condition is satisfied; and perform a mobility to the targetcell based on that the entering condition is satisfied for at least atime to trigger (TTT) related to the mobility execution condition.

According to an embodiment of the present disclosure, a method performedby a base station (BS) in a wireless communication system comprises:transmitting, to a wireless device, a conditional mobility commandcomprising a mobility execution condition for a target cell, wherein thewireless device is configured to: detect that an entering condition ofthe mobility execution condition is satisfied while a timer is running,wherein a radio link failure (RLF) is detected upon an expiry of thetimer; stop the timer based on detecting that the entering condition ofthe mobility execution condition is satisfied; and perform a mobility tothe target cell based on that the entering condition is satisfied for atleast a time to trigger (TTT) related to the mobility executioncondition.

According to an embodiment of the present disclosure, a base station(BS) in a wireless communication system comprises: a transceiver; amemory; and at least one processor operatively coupled to thetransceiver and the memory, and configured to: control the transceiverto transmit, to a wireless device, a conditional mobility commandcomprising a mobility execution condition for a target cell, wherein thewireless device is configured to: detect that an entering condition ofthe mobility execution condition is satisfied while a timer is running,wherein a radio link failure (RLF) is detected upon an expiry of thetimer; stop the timer based on detecting that the entering condition ofthe mobility execution condition is satisfied; and perform a mobility tothe target cell based on that the entering condition is satisfied for atleast a time to trigger (TTT) related to the mobility executioncondition.

According to an embodiment of the present disclosure, a processor for awireless device in a wireless communication system is configured tocontrol the wireless device to perform operations comprising: receivinga conditional mobility command comprising a mobility execution conditionfor a target cell; detecting that an entering condition of the mobilityexecution condition is satisfied while a timer is running, wherein aradio link failure (RLF) is detected upon an expiry of the timer;stopping the timer based on detecting that the entering condition of themobility execution condition is satisfied; and performing a mobility tothe target cell based on that the entering condition is satisfied for atleast a time to trigger (TTT) related to the mobility executioncondition.

According to an embodiment of the present disclosure, acomputer-readable medium having recorded thereon a program forperforming each step of a method on a computer is provided. The methodcomprises: receiving a conditional mobility command comprising amobility execution condition for a target cell; detecting that anentering condition of the mobility execution condition is satisfiedwhile a timer is running, wherein a radio link failure (RLF) is detectedupon an expiry of the timer; stopping the timer based on detecting thatthe entering condition of the mobility execution condition is satisfied;and performing a mobility to the target cell based on that the enteringcondition is satisfied for at least a time to trigger (TTT) related tothe mobility execution condition.

3. Advantageous Effect

The present disclosure can have various advantageous effects.

For example, UE may not start the timer for early RLF declarationif/when an entry condition of a mobility condition for a conditionalmobility is fulfilled for a candidate cell. Also, the UE may stop thetimer for early RLF declaration if/when an entry condition of a mobilitycondition for a conditional mobility is fulfilled for the candidate cellwhile the timer is running. Therefore, the UE can complete theconditional mobility without RLF declaration, so the serviceinterruption time spent on the RRC connection recovery can be avoided.

Advantageous effects which can be obtained through specific embodimentsof the present disclosure are not limited to the advantageous effectslisted above. For example, there may be a variety of technical effectsthat a person having ordinary skill in the related art can understandand/or derive from the present disclosure. Accordingly, the specificeffects of the present disclosure are not limited to those explicitlydescribed herein, but may include various effects that may be understoodor derived from the technical features of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows examples of 5G usage scenarios to which the technicalfeatures of the present disclosure can be applied.

FIG. 2 shows an example of a wireless communication system to which thetechnical features of the present disclosure can be applied.

FIG. 3 shows an example of a wireless communication system to which thetechnical features of the present disclosure can be applied.

FIG. 4 shows another example of a wireless communication system to whichthe technical features of the present disclosure can be applied.

FIG. 5 shows a block diagram of a user plane protocol stack to which thetechnical features of the present disclosure can be applied.

FIG. 6 shows a block diagram of a control plane protocol stack to whichthe technical features of the present disclosure can be applied.

FIG. 7 illustrates a frame structure in a 3GPP based wirelesscommunication system.

FIG. 8 illustrates a data flow example in the 3GPP NR system.

FIG. 9 shows an example of a method for a measurement and reporting towhich technical features of the present disclosure can be applied.

FIG. 10 shows an example of a conditional mobility procedure to whichtechnical features of the present disclosure can be applied.

FIG. 11 shows an example of a case in which a measurement report istriggered after an entry condition for CHO is met.

FIG. 12 shows an example of a case in which a measurement report istriggered before an entry condition for CHO is met.

FIG. 13 shows an example of a method for handling a timer related to RLFaccording to an embodiment of the present disclosure.

FIG. 14 shows another example of a method for handling a timer relatedto RLF according to an embodiment of the present disclosure.

FIG. 15 shows an example of a signal flow for handling a timer relatedto RLF according to an embodiment of the present disclosure.

FIG. 16 shows an example of a T312 timer handling in a mobilityaccording to an embodiment of the present disclosure.

FIG. 17 shows a UE to implement an embodiment of the present disclosure.

FIG. 18 shows another example of a wireless communication system towhich the technical features of the present disclosure can be applied.

FIG. 19 shows an example of an AI device to which the technical featuresof the present disclosure can be applied.

FIG. 20 shows an example of an AI system to which the technical featuresof the present disclosure can be applied.

DETAILED DESCRIPTION

The technical features described below may be used by a communicationstandard by the 3rd generation partnership project (3GPP)standardization organization, a communication standard by the instituteof electrical and electronics engineers (IEEE), etc. For example, thecommunication standards by the 3GPP standardization organization includelong-term evolution (LTE) and/or evolution of LTE systems. The evolutionof LTE systems includes LTE-advanced (LTE-A), LTE-A Pro, and/or 5G newradio (NR). The communication standard by the IEEE standardizationorganization includes a wireless local area network (WLAN) system suchas IEEE 802.11a/b/g/n/ac/ax. The above system uses various multipleaccess technologies such as orthogonal frequency division multipleaccess (OFDMA) and/or single carrier frequency division multiple access(SC-FDMA) for downlink (DL) and/or uplink (UL). For example, only OFDMAmay be used for DL and only SC-FDMA may be used for UL. Alternatively,OFDMA and SC-FDMA may be used for DL and/or UL.

Here, the radio communication technologies implemented in the wirelessdevices in the present disclosure may include narrowbandinternet-of-things (NB-IoT) technology for low-power communication aswell as LTE, NR and 6G. For example, NB-IoT technology may be an exampleof low power wide area network (LPWAN) technology, may be implemented inspecifications such as LTE Cat NB1 and/or LTE Cat NB2, and may not belimited to the above-mentioned names. Additionally and/or alternatively,the radio communication technologies implemented in the wireless devicesin the present disclosure may communicate based on LTE-M technology. Forexample, LTE-M technology may be an example of LPWAN technology and becalled by various names such as enhanced machine type communication(eMTC). For example, LTE-M technology may be implemented in at least oneof the various specifications, such as 1) LTE Cat 0, 2) LTE Cat M1, 3)LTE Cat M2, 4) LTE non-bandwidth limited (non-BL), 5) LTE-MTC, 6) LTEMachine Type Communication, and/or 7) LTE M, and may not be limited tothe above-mentioned names. Additionally and/or alternatively, the radiocommunication technologies implemented in the wireless devices in thepresent disclosure may include at least one of ZigBee, Bluetooth, and/orLPWAN which take into account low-power communication, and may not belimited to the above-mentioned names. For example, ZigBee technology maygenerate personal area networks (PANs) associated with small/low-powerdigital communication based on various specifications such as IEEE802.15.4 and may be called various names.

In the present disclosure, “A or B” may mean “only A”, “only B”, or“both A and B”. In other words, “A or B” in the present disclosure maybe interpreted as “A and/or B”. For example, “A, B or C” in the presentdisclosure may mean “only A”, “only B”, “only C”, or “any combination ofA, B and C”.

In the present disclosure, slash (/) or comma (,) may mean “and/or”. Forexample, “A/B” may mean “A and/or B”. Accordingly, “A/B” may mean “onlyA”, “only B”, or “both A and B”. For example, “A, B, C” may mean “A, Bor C”.

In the present disclosure, “at least one of A and B” may mean “only A”,“only B” or “both A and B”. In addition, the expression “at least one ofA or B” or “at least one of A and/or B” in the present disclosure may beinterpreted as same as “at least one of A and B”.

In addition, in the present disclosure, “at least one of A, B and C” maymean “only A”, “only B”, “only C”, or “any combination of A, B and C”.In addition, “at least one of A, B or C” or “at least one of A, B and/orC” may mean “at least one of A, B and C”.

Also, parentheses used in the present disclosure may mean “for example”.In detail, when it is shown as “control information (PDCCH)”, “PDCCH”may be proposed as an example of “control information”. In other words,“control information” in the present disclosure is not limited to“PDCCH”, and “PDDCH” may be proposed as an example of “controlinformation”. In addition, even when shown as “control information(i.e., PDCCH)”, “PDCCH” may be proposed as an example of “controlinformation”.

Technical features that are separately described in one drawing in thepresent disclosure may be implemented separately or simultaneously.

The terms used throughout the disclosure can be defined as thefollowings:

‘Mobility’ refers to a procedure for i) changing a PCell of a UE (i.e.,handover or PCell change), ii) changing a PSCell of a UE (i.e., SNchange or PSCell change), and/or iii) adding a PSCell for a UE (i.e., SNaddition or PSCell addition). Therefore, the mobility may comprise atleast one of a handover, an SN change or an SN addition. In other words,the mobility may comprise at least one of PCell change, PSCell change orPSCell addition. Throughout the disclosure, performing a mobility to atarget cell may refer to applying a mobility command of the target cellor applying a target cell configuration for the target cell in themobility command of the target cell. The target cell configuration forthe target cell may comprise RRC reconfiguration parameters associatedwith the mobility to the target cell. Further, RRC reconfiguration andRRC connection reconfiguration may be used interchangeably.

‘SN mobility’ refers to a procedure for i) changing a PSCell of a UE(i.e., SN change or PSCell change), and/or ii) adding a PSCell for a UE(i.e., SN addition or PSCell addition). Therefore, the SN mobility maycomprise at least one of an SN change or an SN addition. In other words,the SN mobility may comprise at least one of PSCell change or PSCelladdition. Throughout the disclosure, performing an SN mobility to atarget cell may refer to applying an SN mobility command of the targetcell or applying a target cell configuration for the target cell in theSN mobility command of the target cell. The target cell configurationfor the target cell may comprise RRC reconfiguration parametersassociated with the SN mobility to the target cell. The SN mobility maybe a kind of a mobility. The SN mobility command may comprise a SNchange command for performing SN change, or SN addition command forperforming SN addition.

‘Mobility condition for a target cell’ refers to a triggering conditionfor a mobility to the target cell. That is, the mobility condition for atarget cell refers to a condition that should be satisfied fortriggering a mobility to the target cell. Mobility condition maycomprise at least one of an event, time-to-trigger (TTT), offset value,or threshold value(s). The mobility condition for an event may besatisfied if an entering condition (or, also referred to as entrycondition) for the event is satisfied for at least the TTT. For example,the entering condition for event A3 may be satisfied if a signal qualityfor a target cell is better than that for a source cell more than orequal to the offset value. For another example, the entering conditionfor event A5 may be satisfied if a signal quality for a target cell isbetter than a first threshold and a signal quality for a source cell islower than a second threshold. The mobility condition may also bereferred to as an execution condition/conditional executioncondition/conditional mobility execution condition (e.g., CHO executioncondition).

‘SN mobility condition for a target cell’ refers to a triggeringcondition for an SN mobility (i.e., SN addition or SN change) to thetarget cell. That is, the SN mobility condition for a target cell refersto a condition that should be satisfied for triggering an SN mobility tothe target cell. SN mobility condition for a target cell may beclassified as:

i) SN addition condition for a target cell, which refers to a triggeringcondition for an SN addition of the target cell; or

ii) SN change condition for a target cell, which refers to a triggeringcondition for an SN change to the target cell.

SN mobility condition may comprise at least one of an event,time-to-trigger (TTT), offset value, or threshold value(s). The SNmobility condition for an event may be satisfied if an enteringcondition for the event is satisfied for at least the TTT.

For example, SN addition condition may be related to event A4 or eventB1. The entering condition for event A4 or B1 may be satisfied if asignal quality for a target cell is better than a threshold.

For example, SN change condition may be related to event A3 or event A5.The entering condition for event A3 may be satisfied if a signal qualityfor a target cell is better than that for a source PScell more than orequal to the offset value. For another example, the entering conditionfor event A5 may be satisfied if a signal quality for a target cell isbetter than a first threshold and a signal quality for a source PScellis lower than a second threshold.

‘Conditional mobility’ refers to a mobility that is performed to atarget cell which satisfies a triggering condition among a plurality ofcandidate target cells. Throughout the disclosure, performing aconditional mobility to a target cell may refer to applying aconditional mobility command of a target cell which satisfies a mobilitycondition for the target cell among a plurality of candidate targetcells or applying a target cell configuration for the target cell in theconditional mobility command of the target cell which satisfies amobility condition for the target cell among the plurality of candidatetarget cells. The target cell configuration for the target cell maycomprise RRC reconfiguration parameters associated with the conditionalmobility to the target cell.

Throughout the disclosure, the terms ‘radio access network (RAN) node’,‘base station’, ‘eNB’, ‘gNB’ and ‘cell’ may be used interchangeably.Further, a UE may be a kind of a wireless device, and throughout thedisclosure, the terms ‘UE’ and ‘wireless device’ may be usedinterchangeably.

Throughout the disclosure, the terms ‘cell quality’, ‘signal strength’,‘signal quality’, ‘channel state’, ‘channel quality’, ‘ channelstate/reference signal received power (RSRP)’ and ‘ reference signalreceived quality (RSRQ)’ may be used interchangeably.

The following drawings are created to explain specific embodiments ofthe present disclosure. The names of the specific devices or the namesof the specific signals/messages/fields shown in the drawings areprovided by way of example, and thus the technical features of thepresent disclosure are not limited to the specific names used in thefollowing drawings.

FIG. 1 shows examples of 5G usage scenarios to which the technicalfeatures of the present disclosure can be applied.

The 5G usage scenarios shown in FIG. 1 are only exemplary, and thetechnical features of the present disclosure can be applied to other 5Gusage scenarios which are not shown in FIG. 1 .

Referring to FIG. 1 , the three main requirements areas of 5G include(1) enhanced mobile broadband (eMBB) domain, (2) massive machine typecommunication (mMTC) area, and (3) ultra-reliable and low latencycommunications (URLLC) area. Some use cases may require multiple areasfor optimization and, other use cases may only focus on only one keyperformance indicator (KPI). 5G is to support these various use cases ina flexible and reliable way.

eMBB focuses on across-the-board enhancements to the data rate, latency,user density, capacity and coverage of mobile broadband access. The eMBBaims ˜10 Gbps of throughput. eMBB far surpasses basic mobile Internetaccess and covers rich interactive work and media and entertainmentapplications in cloud and/or augmented reality. Data is one of the keydrivers of 5G and may not be able to see dedicated voice services forthe first time in the 5G era. In 5G, the voice is expected to beprocessed as an application simply using the data connection provided bythe communication system. The main reason for the increased volume oftraffic is an increase in the size of the content and an increase in thenumber of applications requiring high data rates. Streaming services(audio and video), interactive video and mobile Internet connectivitywill become more common as more devices connect to the Internet. Many ofthese applications require always-on connectivity to push real-timeinformation and notifications to the user. Cloud storage andapplications are growing rapidly in mobile communication platforms,which can be applied to both work and entertainment. Cloud storage is aspecial use case that drives growth of uplink data rate. 5G is also usedfor remote tasks on the cloud and requires much lower end-to-end delayto maintain a good user experience when the tactile interface is used.In entertainment, for example, cloud games and video streaming areanother key factor that increases the demand for mobile broadbandcapabilities. Entertainment is essential in smartphones and tabletsanywhere, including high mobility environments such as trains, cars andairplanes. Another use case is augmented reality and informationretrieval for entertainment. Here, augmented reality requires very lowlatency and instantaneous data amount.

mMTC is designed to enable communication between devices that arelow-cost, massive in number and battery-driven, intended to supportapplications such as smart metering, logistics, and field and bodysensors. mMTC aims ˜10 years on battery and/or ˜1 million devices/km2.mMTC allows seamless integration of embedded sensors in all areas and isone of the most widely used 5G applications. Potentially by 2020,internet-of-things (IoT) devices are expected to reach 20.4 billion.Industrial IoT is one of the areas where 5G plays a key role in enablingsmart cities, asset tracking, smart utilities, agriculture and securityinfrastructures.

URLLC will make it possible for devices and machines to communicate withultra-reliability, very low latency and high availability, making itideal for vehicular communication, industrial control, factoryautomation, remote surgery, smart grids and public safety applications.URLLC aims ˜1 ms of latency. URLLC includes new services that willchange the industry through links with ultra-reliability/low latency,such as remote control of key infrastructure and self-driving vehicles.The level of reliability and latency is essential for smart gridcontrol, industrial automation, robotics, drones control andcoordination.

Next, a plurality of use cases included in the triangle of FIG. 1 willbe described in more detail.

5G can complement fiber-to-the-home (FTTH) and cable-based broadband (orDOCSIS) as a means of delivering streams rated from hundreds of megabitsper second to gigabits per second. This high speed can be required todeliver TVs with resolutions of 4K or more (6K, 8K and above) as well asvirtual reality (VR) and augmented reality (AR). VR and AR applicationsinclude mostly immersive sporting events. Certain applications mayrequire special network settings. For example, in the case of a VR game,a game company may need to integrate a core server with an edge networkserver of a network operator to minimize delay.

Automotive is expected to become an important new driver for 5G, withmany use cases for mobile communications to vehicles. For example,entertainment for passengers demands high capacity and high mobilebroadband at the same time. This is because future users will continueto expect high-quality connections regardless of their location andspeed. Another use case in the automotive sector is an augmented realitydashboard. The driver can identify an object in the dark on top of whatis being viewed through the front window through the augmented realitydashboard. The augmented reality dashboard displays information thatwill inform the driver about the object's distance and movement. In thefuture, the wireless module enables communication between vehicles,information exchange between the vehicle and the supportinginfrastructure, and information exchange between the vehicle and otherconnected devices (e.g. devices accompanied by a pedestrian). The safetysystem allows the driver to guide the alternative course of action sothat he can drive more safely, thereby reducing the risk of accidents.The next step will be a remotely controlled vehicle or self-drivingvehicle. This requires a very reliable and very fast communicationbetween different self-driving vehicles and between vehicles andinfrastructure. In the future, a self-driving vehicle will perform alldriving activities, and the driver will focus only on traffic that thevehicle itself cannot identify. The technical requirements ofself-driving vehicles require ultra-low latency and high-speedreliability to increase traffic safety to a level not achievable byhumans.

Smart cities and smart homes, which are referred to as smart societies,will be embedded in high density wireless sensor networks. Thedistributed network of intelligent sensors will identify conditions forcost and energy-efficient maintenance of a city or house. A similarsetting can be performed for each home. Temperature sensors, windows andheating controllers, burglar alarms and appliances are all wirelesslyconnected. Many of these sensors typically require low data rate, lowpower and low cost. However, for example, real-time high-definition (HD)video may be required for certain types of devices for monitoring.

The consumption and distribution of energy, including heat or gas, ishighly dispersed, requiring automated control of distributed sensornetworks. The smart grid interconnects these sensors using digitalinformation and communication technologies to collect and act oninformation. This information can include supplier and consumerbehavior, allowing the smart grid to improve the distribution of fuel,such as electricity, in terms of efficiency, reliability, economy,production sustainability, and automated methods. The smart grid can beviewed as another sensor network with low latency.

The health sector has many applications that can benefit from mobilecommunications. Communication systems can support telemedicine toprovide clinical care in remote locations. This can help to reducebarriers to distance and improve access to health services that are notcontinuously available in distant rural areas. It is also used to savelives in critical care and emergency situations. Mobile communicationbased wireless sensor networks can provide remote monitoring and sensorsfor parameters such as heart rate and blood pressure.

Wireless and mobile communications are becoming increasingly importantin industrial applications. Wiring costs are high for installation andmaintenance. Thus, the possibility of replacing a cable with a wirelesslink that can be reconfigured is an attractive opportunity in manyindustries. However, achieving this requires that wireless connectionsoperate with similar delay, reliability, and capacity as cables and thattheir management is simplified. Low latency and very low errorprobabilities are new requirements that need to be connected to 5G.

Logistics and freight tracking are important use cases of mobilecommunications that enable tracking of inventory and packages anywhereusing location based information systems. Use cases of logistics andfreight tracking typically require low data rates, but require a largerange and reliable location information.

NR supports multiple numerology (or, subcarrier spacing (SCS)) tosupport various 5G services. For example, when the SCS is 15 kHz, widearea in traditional cellular bands may be supported. When the SCS is 30kHz/60 kHz, dense-urban, lower latency and wider carrier bandwidth maybe supported. When the SCS is 60 kHz or higher, a bandwidth greater than24.25 GHz may be supported to overcome phase noise.

The NR frequency band may be defined as two types of frequency range,i.e., FR1 and FR2. The numerical value of the frequency range may bechanged. For example, the frequency ranges of the two types (FR1 andFR2) may be as shown in Table 1 below. For ease of explanation, in thefrequency ranges used in the NR system, FR1 may mean “sub 6 GHz range”,FR2 may mean “above 6 GHz range,” and may be referred to as millimeterwave (mmW).

TABLE 1 Frequency Range Corresponding designation frequency rangeSubcarrier Spacing FR1  450 MHz-6000 MHz  15, 30, 60 kHz FR2 24250MHz-52600 MHz 60, 120, 240 kHz

As mentioned above, the numerical value of the frequency range of the NRsystem may be changed. For example, FR1 may include a frequency band of410 MHz to 7125 MHz as shown in Table 2 below. That is, FR1 may includea frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or more. Forexample, a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) ormore included in FR1 may include an unlicensed band. Unlicensed bandsmay be used for a variety of purposes, for example for communication forvehicles (e.g., autonomous driving).

TABLE 2 Frequency Range Corresponding designation frequency rangeSubcarrier Spacing FR1  410 MHz-7125 MHz  15, 30, 60 kHz FR2 24250MHz-52600 MHz 60, 120, 240 kHz

FIG. 2 shows an example of a wireless communication system to which thetechnical features of the present disclosure can be applied. Referringto FIG. 2 , the wireless communication system may include a first device210 and a second device 220.

The first device 210 includes a base station, a network node, atransmitting UE, a receiving UE, a wireless device, a wirelesscommunication device, a vehicle, a vehicle equipped with an autonomousdriving function, a connected car, a drone, an unmanned aerial vehicle(UAV), an artificial intelligence (AI) module, a robot, an AR device, aVR device, a mixed reality (MR) device, a hologram device, a publicsafety device, an MTC device, an IoT device, a medical device, afin-tech device (or, a financial device), a security device, aclimate/environmental device, a device related to 5G services, or adevice related to the fourth industrial revolution.

The second device 220 includes a base station, a network node, atransmitting UE, a receiving UE, a wireless device, a wirelesscommunication device, a vehicle, a vehicle equipped with an autonomousdriving function, a connected car, a drone, a UAV, an AI module, arobot, an AR device, a VR device, an MR device, a hologram device, apublic safety device, an MTC device, an IoT device, a medical device, afin-tech device (or, a financial device), a security device, aclimate/environmental device, a device related to 5G services, or adevice related to the fourth industrial revolution.

For example, the UE may include a mobile phone, a smart phone, a laptopcomputer, a digital broadcasting terminal, a personal digital assistant(PDA), a portable multimedia player (PMP), a navigation device, a slatepersonal computer (PC), a tablet PC, an ultrabook, a wearable device(e.g. a smartwatch, a smart glass, a head mounted display (HMD)). Forexample, the HMD may be a display device worn on the head. For example,the HMD may be used to implement AR, VR and/or MR.

For example, the drone may be a flying object that is flying by a radiocontrol signal without a person boarding it. For example, the VR devicemay include a device that implements an object or background in thevirtual world. For example, the AR device may include a device thatimplements connection of an object and/or a background of a virtualworld to an object and/or a background of the real world. For example,the MR device may include a device that implements fusion of an objectand/or a background of a virtual world to an object and/or a backgroundof the real world. For example, the hologram device may include a devicethat implements a 360-degree stereoscopic image by recording and playingstereoscopic information by utilizing a phenomenon of interference oflight generated by the two laser lights meeting with each other, calledholography. For example, the public safety device may include a videorelay device or a video device that can be worn by the user's body. Forexample, the MTC device and the IoT device may be a device that do notrequire direct human intervention or manipulation. For example, the MTCdevice and the IoT device may include a smart meter, a vending machine,a thermometer, a smart bulb, a door lock and/or various sensors. Forexample, the medical device may be a device used for the purpose ofdiagnosing, treating, alleviating, handling, or preventing a disease.For example, the medical device may be a device used for the purpose ofdiagnosing, treating, alleviating, or correcting an injury or disorder.For example, the medical device may be a device used for the purpose ofinspecting, replacing or modifying a structure or function. For example,the medical device may be a device used for the purpose of controllingpregnancy. For example, the medical device may include a treatmentdevice, a surgical device, an (in vitro) diagnostic device, a hearingaid and/or a procedural device, etc. For example, a security device maybe a device installed to prevent the risk that may occur and to maintainsafety. For example, the security device may include a camera, aclosed-circuit TV (CCTV), a recorder, or a black box. For example, thefin-tech device may be a device capable of providing financial servicessuch as mobile payment. For example, the fin-tech device may include apayment device or a point of sales (POS). For example, theclimate/environmental device may include a device for monitoring orpredicting the climate/environment.

The first device 210 may include at least one or more processors, suchas a processor 211, at least one memory, such as a memory 212, and atleast one transceiver, such as a transceiver 213. The processor 211 mayperform the functions, procedures, and/or methods of the first devicedescribed throughout the disclosure. The processor 211 may perform oneor more protocols. For example, the processor 211 may perform one ormore layers of the air interface protocol. The memory 212 is connectedto the processor 211 and may store various types of information and/orinstructions. The transceiver 213 is connected to the processor 211 andmay be controlled by the processor 211 to transmit and receive wirelesssignals.

The second device 220 may include at least one or more processors, suchas a processor 221, at least one memory, such as a memory 222, and atleast one transceiver, such as a transceiver 223. The processor 221 mayperform the functions, procedures, and/or methods of the second device220 described throughout the disclosure. The processor 221 may performone or more protocols. For example, the processor 221 may perform one ormore layers of the air interface protocol. The memory 222 is connectedto the processor 221 and may store various types of information and/orinstructions. The transceiver 223 is connected to the processor 221 andmay be controlled by the processor 221 to transmit and receive wirelesssignals.

The memory 212, 222 may be connected internally or externally to theprocessor 211, 212, or may be connected to other processors via avariety of technologies such as wired or wireless connections.

The first device 210 and/or the second device 220 may have more than oneantenna. For example, antenna 214 and/or antenna 224 may be configuredto transmit and receive wireless signals.

FIG. 3 shows an example of a wireless communication system to which thetechnical features of the present disclosure can be applied.

Specifically, FIG. 3 shows a system architecture based on anevolved-UMTS terrestrial radio access network (E-UTRAN). Theaforementioned LTE is a part of an evolved-UTMS (e-UMTS) using theE-UTRAN.

Referring to FIG. 3 , the wireless communication system includes one ormore user equipment (UE) 310, an E-UTRAN and an evolved packet core(EPC). The UE 310 refers to a communication equipment carried by a user.The UE 310 may be fixed or mobile. The UE 310 may be referred to asanother terminology, such as a mobile station (MS), a user terminal(UT), a subscriber station (SS), a wireless device, etc.

The E-UTRAN consists of one or more evolved NodeB (eNB) 320. The eNB 320provides the E-UTRA user plane and control plane protocol terminationstowards the UE 10. The eNB 320 is generally a fixed station thatcommunicates with the UE 310. The eNB 320 hosts the functions, such asinter-cell radio resource management (RRM), radio bearer (RB) control,connection mobility control, radio admission control, measurementconfiguration/provision, dynamic resource allocation (scheduler), etc.The eNB 320 may be referred to as another terminology, such as a basestation (BS), a base transceiver system (BTS), an access point (AP),etc.

A downlink (DL) denotes communication from the eNB 320 to the UE 310. Anuplink (UL) denotes communication from the UE 310 to the eNB 320. Asidelink (SL) denotes communication between the UEs 310. In the DL, atransmitter may be a part of the eNB 320, and a receiver may be a partof the UE 310. In the UL, the transmitter may be a part of the UE 310,and the receiver may be a part of the eNB 320. In the SL, thetransmitter and receiver may be a part of the UE 310.

The EPC includes a mobility management entity (MME), a serving gateway(S-GW) and a packet data network (PDN) gateway (P-GW). The MME hosts thefunctions, such as non-access stratum (NAS) security, idle statemobility handling, evolved packet system (EPS) bearer control, etc. TheS-GW hosts the functions, such as mobility anchoring, etc. The S-GW is agateway having an E-UTRAN as an endpoint. For convenience, MME/S-GW 330will be referred to herein simply as a “gateway,” but it is understoodthat this entity includes both the MME and S-GW. The P-GW hosts thefunctions, such as UE Internet protocol (IP) address allocation, packetfiltering, etc. The P-GW is a gateway having a PDN as an endpoint. TheP-GW is connected to an external network.

The UE 310 is connected to the eNB 320 by means of the Uu interface. TheUEs 310 are interconnected with each other by means of the PC5interface. The eNBs 320 are interconnected with each other by means ofthe X2 interface. The eNBs 320 are also connected by means of the S1interface to the EPC, more specifically to the MME by means of theS1-MME interface and to the S-GW by means of the S1-U interface. The S1interface supports a many-to-many relation between MMEs/S-GWs and eNBs.

FIG. 4 shows another example of a wireless communication system to whichthe technical features of the present disclosure can be applied.

Specifically, FIG. 4 shows a system architecture based on a 5G NR. Theentity used in the 5G NR (hereinafter, simply referred to as “NW”) mayabsorb some or all of the functions of the entities introduced in FIG. 3(e.g. eNB, MME, S-GW). The entity used in the NR may be identified bythe name “NG” for distinction from the LTE/LTE-A.

Referring to FIG. 4 , the wireless communication system includes one ormore UE 410, a next-generation RAN (NG-RAN) and a 5th generation corenetwork (5GC). The NG-RAN consists of at least one NG-RAN node. TheNG-RAN node is an entity corresponding to the eNB 320 shown in FIG. 3 .The NG-RAN node consists of at least one gNB 421 and/or at least oneng-eNB 422. The gNB 421 provides NR user plane and control planeprotocol terminations towards the UE 410. The ng-eNB 422 provides E-UTRAuser plane and control plane protocol terminations towards the UE 410.

The 5GC includes an access and mobility management function (AMF), auser plane function (UPF) and a session management function (SMF). TheAMF hosts the functions, such as NAS security, idle state mobilityhandling, etc. The AMF is an entity including the functions of theconventional MME. The UPF hosts the functions, such as mobilityanchoring, protocol data unit (PDU) handling. The UPF an entityincluding the functions of the conventional S-GW. The SMF hosts thefunctions, such as UE IP address allocation, PDU session control.

The gNBs 421 and ng-eNBs 422 are interconnected with each other by meansof the Xn interface. The gNBs 421 and ng-eNBs 422 are also connected bymeans of the NG interfaces to the 5GC, more specifically to the AMF bymeans of the NG-C interface and to the UPF by means of the NG-Uinterface.

A protocol structure between network entities described above isdescribed. On the system of FIG. 3 and/or FIG. 4 , layers of a radiointerface protocol between the UE and the network (e.g. NG-RAN and/orE-UTRAN) may be classified into a first layer (L1), a second layer (L2),and a third layer (L3) based on the lower three layers of the opensystem interconnection (OSI) model that is well-known in thecommunication system.

FIG. 5 shows a block diagram of a user plane protocol stack to which thetechnical features of the present disclosure can be applied. FIG. 6shows a block diagram of a control plane protocol stack to which thetechnical features of the present disclosure can be applied.

The user/control plane protocol stacks shown in FIG. 5 and FIG. 6 areused in NR. However, user/control plane protocol stacks shown in FIG. 5and FIG. 6 may be used in LTE/LTE-A without loss of generality, byreplacing gNB/AMF with eNB/MME.

Referring to FIG. 5 and FIG. 6 , a physical (PHY) layer belonging to L1.The PHY layer offers information transfer services to media accesscontrol (MAC) sublayer and higher layers. The PHY layer offers to theMAC sublayer transport channels. Data between the MAC sublayer and thePHY layer is transferred via the transport channels. Between differentPHY layers, i.e., between a PHY layer of a transmission side and a PHYlayer of a reception side, data is transferred via the physicalchannels.

The MAC sublayer belongs to L2. The main services and functions of theMAC sublayer include mapping between logical channels and transportchannels, multiplexing/de-multiplexing of MAC service data units (SDUs)belonging to one or different logical channels into/from transportblocks (TB) delivered to/from the physical layer on transport channels,scheduling information reporting, error correction through hybridautomatic repeat request (HARQ), priority handling between UEs by meansof dynamic scheduling, priority handling between logical channels of oneUE by means of logical channel prioritization (LCP), etc. The MACsublayer offers to the radio link control (RLC) sublayer logicalchannels.

The RLC sublayer belong to L2. The RLC sublayer supports threetransmission modes, i.e. transparent mode (TM), unacknowledged mode(UM), and acknowledged mode (AM), in order to guarantee various qualityof services (QoS) required by radio bearers. The main services andfunctions of the RLC sublayer depend on the transmission mode. Forexample, the RLC sublayer provides transfer of upper layer PDUs for allthree modes, but provides error correction through ARQ for AM only. InLTE/LTE-A, the RLC sublayer provides concatenation, segmentation andreassembly of RLC SDUs (only for UM and AM data transfer) andre-segmentation of RLC data PDUs (only for AM data transfer). In NR, theRLC sublayer provides segmentation (only for AM and UM) andre-segmentation (only for AM) of RLC SDUs and reassembly of SDU (onlyfor AM and UM). That is, the NR does not support concatenation of RLCSDUs. The RLC sublayer offers to the packet data convergence protocol(PDCP) sublayer RLC channels.

The PDCP sublayer belong to L2. The main services and functions of thePDCP sublayer for the user plane include header compression anddecompression, transfer of user data, duplicate detection, PDCP PDUrouting, retransmission of PDCP SDUs, ciphering and deciphering, etc.The main services and functions of the PDCP sublayer for the controlplane include ciphering and integrity protection, transfer of controlplane data, etc.

The service data adaptation protocol (SDAP) sublayer belong to L2. TheSDAP sublayer is only defined in the user plane. The SDAP sublayer isonly defined for NR. The main services and functions of SDAP include,mapping between a QoS flow and a data radio bearer (DRB), and markingQoS flow ID (QFI) in both DL and UL packets. The SDAP sublayer offers to5GC QoS flows.

A radio resource control (RRC) layer belongs to L3. The RRC layer isonly defined in the control plane. The RRC layer controls radioresources between the UE and the network. To this end, the RRC layerexchanges RRC messages between the UE and the BS. The main services andfunctions of the RRC layer include broadcast of system informationrelated to AS and NAS, paging, establishment, maintenance and release ofan RRC connection between the UE and the network, security functionsincluding key management, establishment, configuration, maintenance andrelease of radio bearers, mobility functions, QoS management functions,UE measurement reporting and control of the reporting, NAS messagetransfer to/from NAS from/to UE.

In other words, the RRC layer controls logical channels, transportchannels, and physical channels in relation to the configuration,reconfiguration, and release of radio bearers. A radio bearer refers toa logical path provided by L1 (PHY layer) and L2 (MAC/RLC/PDCP/SDAPsublayer) for data transmission between a UE and a network. Setting theradio bearer means defining the characteristics of the radio protocollayer and the channel for providing a specific service, and setting eachspecific parameter and operation method. Radio bearer may be dividedinto signaling RB (SRB) and data RB (DRB). The SRB is used as a path fortransmitting RRC messages in the control plane, and the DRB is used as apath for transmitting user data in the user plane.

An RRC state indicates whether an RRC layer of the UE is logicallyconnected to an RRC layer of the E-UTRAN. In LTE/LTE-A, when the RRCconnection is established between the RRC layer of the UE and the RRClayer of the E-UTRAN, the UE is in the RRC connected state(RRC_CONNECTED). Otherwise, the UE is in the RRC idle state (RRC_IDLE).In NR, the RRC inactive state (RRC_INACTIVE) is additionally introduced.RRC_INACTIVE may be used for various purposes. For example, the massivemachine type communications (MMTC) UEs can be efficiently managed inRRC_INACTIVE. When a specific condition is satisfied, transition is madefrom one of the above three states to the other.

A predetermined operation may be performed according to the RRC state.In RRC_IDLE, public land mobile network (PLMN) selection, broadcast ofsystem information (SI), cell re-selection mobility, core network (CN)paging and discontinuous reception (DRX) configured by NAS may beperformed. The UE shall have been allocated an identifier (ID) whichuniquely identifies the UE in a tracking area. No RRC context stored inthe BS.

In RRC_CONNECTED, the UE has an RRC connection with the network (i.e.E-UTRAN/NG-RAN). Network-CN connection (both C/U-planes) is alsoestablished for UE. The UE AS context is stored in the network and theUE. The RAN knows the cell which the UE belongs to. The network cantransmit and/or receive data to/from UE. Network controlled mobilityincluding measurement is also performed.

Most of operations performed in RRC_IDLE may be performed inRRC_INACTIVE. But, instead of CN paging in RRC_IDLE, RAN paging isperformed in RRC_INACTIVE. In other words, in RRC_IDLE, paging formobile terminated (MT) data is initiated by core network and paging areais managed by core network. In RRC_INACTIVE, paging is initiated byNG-RAN, and RAN-based notification area (RNA) is managed by NG-RAN.Further, instead of DRX for CN paging configured by NAS in RRC_IDLE, DRXfor RAN paging is configured by NG-RAN in RRC_INACTIVE. Meanwhile, inRRC_INACTIVE, 5GC-NG-RAN connection (both C/U-planes) is established forUE, and the UE AS context is stored in NG-RAN and the UE. NG-RAN knowsthe RNA which the UE belongs to.

NAS layer is located at the top of the RRC layer. The NAS controlprotocol performs the functions, such as authentication, mobilitymanagement, security control.

The physical channels may be modulated according to OFDM processing andutilizes time and frequency as radio resources. The physical channelsconsist of a plurality of orthogonal frequency division multiplexing(OFDM) symbols in time domain and a plurality of subcarriers infrequency domain. One subframe consists of a plurality of OFDM symbolsin the time domain. A resource block is a resource allocation unit, andconsists of a plurality of OFDM symbols and a plurality of subcarriers.In addition, each subframe may use specific subcarriers of specific OFDMsymbols (e.g. first OFDM symbol) of the corresponding subframe for aphysical downlink control channel (PDCCH), i.e. L1/L2 control channel. Atransmission time interval (TTI) is a basic unit of time used by ascheduler for resource allocation. The TTI may be defined in units ofone or a plurality of slots, or may be defined in units of mini-slots.

The transport channels are classified according to how and with whatcharacteristics data are transferred over the radio interface. DLtransport channels include a broadcast channel (BCH) used fortransmitting system information, a downlink shared channel (DL-SCH) usedfor transmitting user traffic or control signals, and a paging channel(PCH) used for paging a UE. UL transport channels include an uplinkshared channel (UL-SCH) for transmitting user traffic or control signalsand a random access channel (RACH) normally used for initial access to acell.

Different kinds of data transfer services are offered by MAC sublayer.Each logical channel type is defined by what type of information istransferred. Logical channels are classified into two groups: controlchannels and traffic channels.

Control channels are used for the transfer of control plane informationonly. The control channels include a broadcast control channel (BCCH), apaging control channel (PCCH), a common control channel (CCCH) and adedicated control channel (DCCH). The BCCH is a DL channel forbroadcasting system control information. The PCCH is DL channel thattransfers paging information, system information change notifications.The CCCH is a channel for transmitting control information between UEsand network. This channel is used for UEs having no RRC connection withthe network. The DCCH is a point-to-point bi-directional channel thattransmits dedicated control information between a UE and the network.This channel is used by UEs having an RRC connection.

Traffic channels are used for the transfer of user plane informationonly. The traffic channels include a dedicated traffic channel (DTCH).The DTCH is a point-to-point channel, dedicated to one UE, for thetransfer of user information. The DTCH can exist in both UL and DL.

Regarding mapping between the logical channels and transport channels,in DL, BCCH can be mapped to BCH, BCCH can be mapped to DL-SCH, PCCH canbe mapped to PCH, CCCH can be mapped to DL-SCH, DCCH can be mapped toDL-SCH, and DTCH can be mapped to DL-SCH. In UL, CCCH can be mapped toUL-SCH, DCCH can be mapped to UL-SCH, and DTCH can be mapped to UL-SCH.

FIG. 7 illustrates a frame structure in a 3GPP based wirelesscommunication system.

The frame structure illustrated in FIG. 7 is purely exemplary and thenumber of subframes, the number of slots, and/or the number of symbolsin a frame may be variously changed. In the 3GPP based wirelesscommunication system, an OFDM numerology (e.g., subcarrier spacing(SCS), transmission time interval (TTI) duration) may be differentlyconfigured between a plurality of cells aggregated for one UE. Forexample, if a UE is configured with different SCSs for cells aggregatedfor the cell, an (absolute time) duration of a time resource (e.g. asubframe, a slot, or a TTI) including the same number of symbols may bedifferent among the aggregated cells. Herein, symbols may include OFDMsymbols (or CP-OFDM symbols), SC-FDMA symbols (or discrete Fouriertransform-spread-OFDM (DFT-s-OFDM) symbols).

Referring to FIG. 7 , downlink and uplink transmissions are organizedinto frames. Each frame has Tf=10 ms duration. Each frame is dividedinto two half-frames, where each of the half-frames has 5 ms duration.Each half-frame consists of 5 subframes, where the duration Tsf persubframe is 1 ms. Each subframe is divided into slots and the number ofslots in a subframe depends on a subcarrier spacing. Each slot includes14 or 12 OFDM symbols based on a cyclic prefix (CP). In a normal CP,each slot includes 14 OFDM symbols and, in an extended CP, each slotincludes 12 OFDM symbols. The numerology is based on exponentiallyscalable subcarrier spacing Δf=2u*15 kHz. The following table shows thenumber of OFDM symbols per slot, the number of slots per frame, and thenumber of slots per for the normal CP, according to the subcarrierspacing Δf=2u*15 kHz.

TABLE 3 u Nslotsymb Nframe, uslot Nsubframe, uslot 0 14 10 1 1 14 20 2 214 40 4 3 14 80 8 4 14 160 16

The following table shows the number of OFDM symbols per slot, thenumber of slots per frame, and the number of slots per for the extendedCP, according to the subcarrier spacing Δf=2u*15 kHz.

TABLE 4 u Nslotsymb Nframe, uslot Nsubframe, uslot 2 12 40 4

A slot includes plural symbols (e.g., 14 or 12 symbols) in the timedomain. For each numerology (e.g. subcarrier spacing) and carrier, aresource grid of Nsize,ugrid,x*NRBsc subcarriers and Nsubframe,usymbOFDM symbols is defined, starting at common resource block (CRB)Nstart,ugrid indicated by higher-layer signaling (e.g. radio resourcecontrol (RRC) signaling), where Nsize,ugrid,x is the number of resourceblocks (RBs) in the resource grid and the subscript xis DL for downlinkand UL for uplink. NRBsc is the number of subcarriers per RB. In the3GPP based wireless communication system, NRBsc is 12 generally. Thereis one resource grid for a given antenna port p, subcarrier spacingconfiguration u, and transmission direction (DL or UL). The carrierbandwidth Nsize,ugrid for subcarrier spacing configuration u is given bythe higher-layer parameter (e.g. RRC parameter). Each element in theresource grid for the antenna port p and the subcarrier spacingconfiguration u is referred to as a resource element (RE) and onecomplex symbol may be mapped to each RE. Each RE in the resource grid isuniquely identified by an index k in the frequency domain and an index 1representing a symbol location relative to a reference point in the timedomain. In the 3GPP based wireless communication system, an RB isdefined by 12 consecutive subcarriers in the frequency domain. In the3GPP NR system, RBs are classified into CRBs and physical resourceblocks (PRBs). CRBs are numbered from 0 and upwards in the frequencydomain for subcarrier spacing configuration u. The center of subcarrier0 of CRB 0 for subcarrier spacing configuration u coincides with ‘pointA’ which serves as a common reference point for resource block grids. Inthe 3GPP NR system, PRBs are defined within a bandwidth part (BWP) andnumbered from 0 to NsizeBWP,i−1, where i is the number of the bandwidthpart. The relation between the physical resource block nPRB in thebandwidth part i and the common resource block nCRB is as follows:nPRB=nCRB+NsizeBWP,i, where NsizeBWP,i is the common resource blockwhere bandwidth part starts relative to CRB 0. The BWP includes aplurality of consecutive RBs. A carrier may include a maximum of N(e.g., 5) BWPs. A UE may be configured with one or more BWPs on a givencomponent carrier. Only one BWP among BWPs configured to the UE canactive at a time. The active BWP defines the UE's operating bandwidthwithin the cell's operating bandwidth.

In the present disclosure, the term “cell” may refer to a geographicarea to which one or more nodes provide a communication system, or referto radio resources. A “cell” of a geographic area may be understood ascoverage within which a node can provide service using a carrier and a“cell” as radio resources (e.g. time-frequency resources) is associatedwith bandwidth (BW) which is a frequency range configured by thecarrier. The “cell” associated with the radio resources is defined by acombination of downlink resources and uplink resources, for example, acombination of a downlink (DL) component carrier (CC) and a uplink (UL)CC. The cell may be configured by downlink resources only, or may beconfigured by downlink resources and uplink resources. Since DLcoverage, which is a range within which the node is capable oftransmitting a valid signal, and UL coverage, which is a range withinwhich the node is capable of receiving the valid signal from the UE,depends upon a carrier carrying the signal, the coverage of the node maybe associated with coverage of the “cell” of radio resources used by thenode. Accordingly, the term “cell” may be used to represent servicecoverage of the node sometimes, radio resources at other times, or arange that signals using the radio resources can reach with validstrength at other times.

In carrier aggregation (CA), two or more CCs are aggregated. A UE maysimultaneously receive or transmit on one or multiple CCs depending onits capabilities. CA is supported for both contiguous and non-contiguousCCs. When CA is configured the UE only has one radio resource control(RRC) connection with the network. At RRC connectionestablishment/re-establishment/handover, one serving cell provides thenon-access stratum (NAS) mobility information, and at RRC connectionre-establishment/handover, one serving cell provides the security input.This cell is referred to as the Primary Cell (PCell). The PCell is acell, operating on the primary frequency, in which the UE eitherperforms the initial connection establishment procedure or initiates theconnection re-establishment procedure. Depending on UE capabilities,Secondary Cells (SCells) can be configured to form together with thePCell a set of serving cells. An SCell is a cell providing additionalradio resources on top of Special Cell. The configured set of servingcells for a UE therefore always consists of one PCell and one or moreSCells. For dual connectivity operation, the term Special Cell (SpCell)refers to the PCell of the master cell group (MCG) or the PSCell of thesecondary cell group (SCG). An SpCell supports PUCCH transmission andcontention-based random access, and is always activated. The MCG is agroup of serving cells associated with a master node, comprising of theSpCell (PCell) and optionally one or more SCells. The SCG is the subsetof serving cells associated with a secondary node, comprising of thePSCell and zero or more SCells, for a UE configured with dualconnectivity (DC). For a UE in RRC_CONNECTED not configured with CA/DCthere is only one serving cell comprising of the PCell. For a UE inRRC_CONNECTED configured with CA/DC the term “serving cells” is used todenote the set of cells comprising of the SpCell(s) and all SCells. InDC, two MAC entities are configured in a UE: one for the MCG and one forthe SCG.

FIG. 8 illustrates a data flow example in the 3GPP NR system.

In FIG. 8 , “RB” denotes a radio bearer, and “H” denotes a header. Radiobearers are categorized into two groups: data radio bearers (DRB) foruser plane data and signalling radio bearers (SRB) for control planedata. The MAC PDU is transmitted/received using radio resources throughthe PHY layer to/from an external device. The MAC PDU arrives to the PHYlayer in the form of a transport block.

In the PHY layer, the uplink transport channels UL-SCH and RACH aremapped to their physical channels PUSCH and PRACH, respectively, and thedownlink transport channels DL-SCH, BCH and PCH are mapped to PDSCH,PBCH and PDSCH, respectively. In the PHY layer, uplink controlinformation (UCI) is mapped to PUCCH, and downlink control information(DCI) is mapped to PDCCH. A MAC PDU related to UL-SCH is transmitted bya UE via a PUSCH based on an UL grant, and a MAC PDU related to DL-SCHis transmitted by a BS via a PDSCH based on a DL assignment.

Data unit(s) (e.g. PDCP SDU, PDCP PDU, RLC SDU, RLC PDU, RLC SDU, MACSDU, MAC CE, MAC PDU) in the present disclosure is(are)transmitted/received on a physical channel (e.g. PDSCH, PUSCH) based onresource allocation (e.g. UL grant, DL assignment). In the presentdisclosure, uplink resource allocation is also referred to as uplinkgrant, and downlink resource allocation is also referred to as downlinkassignment. The resource allocation includes time domain resourceallocation and frequency domain resource allocation. In the presentdisclosure, an uplink grant is either received by the UE dynamically onPDCCH, in a Random Access Response, or configured to the UEsemi-persistently by RRC. In the present disclosure, downlink assignmentis either received by the UE dynamically on the PDCCH, or configured tothe UE semi-persistently by RRC signalling from the BS.

FIG. 9 shows an example of a method for a measurement and reporting towhich technical features of the present disclosure can be applied.

Referring to FIG. 9 , in step S901, a UE may receive a measurementconfiguration from a RAN node. The measurement configuration maycomprise a list of measurement objects (measObject), a list of reportconfigurations (reportConfig), and a list of measurement identifiers ID,measID). The measurement ID may be related to/correspond to acombination of a measurement object and a report configuration. Themeasurement object may indicate object information regarding an objectthe UE is supposed to measure. For example, the object information maycomprise a measurement frequency and/or a list of cells includingserving cell/neighbor cell(s). The report configuration may comprise acondition to perform an action corresponding to a report type in thereport configuration. For example, the condition may comprise a reportcondition that should be satisfied for the UE to transmit a measurementreport. For another example, the condition may comprise a mobilitycondition that should be satisfied for the UE to perform a conditionalmobility. If the report type is set to ‘condTriggerConfig’, thecondition may be the mobility condition. The report type may also bereferred to as a purpose of the condition.

In step S903, the UE may perform a measurement based on the measurementconfiguration. For example, the UE may measure the serving cell and/orthe neighbor cell(s) on the measurement frequency specified by themeasurement object, to obtain a measurement result for the serving celland/or the neighbor cell(s). The measurement result may comprise a cellquality/signal strength/signal quality/channel quality/channelstate/reference signal received power (RSRP)/reference signal receivedquality (RSRQ) of the serving cell and/or the neighbor cell(s).

In step S905, the UE may transmit a measurement report to the RAN node.The UE may transmit the measurement report comprising the measurementresult for the serving cell and/or the neighbor cell(s) to the RAN nodebased on the report configuration (e.g., when the report condition issatisfied).

According to various embodiments, the report condition may comprise atleast one of an event, time-to-trigger (TTT), offset value, or thresholdvalue 9s). The report condition for an event may be satisfied if anentering condition for the event is satisfied for at least the TTT. Forexample, the entering condition for event A1 may be satisfied if a cellquality of a serving cell becomes better than a threshold. The enteringcondition for event A2 may be satisfied if a cell quality of a servingcell becomes worse than a threshold. The entering condition for event A3may be satisfied if a cell quality of a neighbor cell becomes betterthan that of a serving cell by an offset. The entering condition forevent A4 may be satisfied if a cell quality of a neighbor cell becomesbetter than a threshold. The entering condition for event A5 may besatisfied if a cell quality of a serving cell becomes worse than aserving cell threshold, and a cell quality of a neighbor cell becomesbetter than a neighbor cell threshold.

According to various embodiments, the measurement configuration maycomprise/be related to at least one of a measurement period, ameasurement gap, or a measurement gap repetition period. The measurementperiod refers to a time spacing between two consecutive moments at whicha measurement on a neighbor cell is performed and/or a cell quality ofthe neighbor cell is obtained. The measurement gap refers to a gap/timeperiod during which no transmission and reception happens for the UE tomeasure a neighbor cell/inter-frequency. The measurement gap repetitionperiod refers to a time interval in which successive measurement gapsrepetitively occurs. In other words, the measurement gap repetitionperiod refers to a time interval between successive measurement gaps.

According to various embodiments, the measurement configuration maycomprise a configuration parameter ‘s-MeasureConfig’. Thes-MeasureConfig may be a threshold for NR SpCell RSRP measurementcontrolling when the UE is required to perform measurements onnon-serving cells. If the s-MeasureConfig is set to ssb-RSRP, thethreshold may be cell RSRP based on SS/PBCH block. If thes-MeasureConfig is set to csi-RSRP, the threshold may be cell RSRP ofCSI-RS.

Hereinafter, conditional mobility is described.

A conditional mobility may be adopted to avoid a mobility failure thatmay happen due to, for example, a reception of mobility failure. In aconditional mobility, UE may receive a conditional mobility commandprior to actual mobility timing so as to increase the probability ofsuccessful mobility. The conditional mobility command may includemobility execution condition(s) and target cell configuration(s) each ofwhich corresponds to the different target cell(s) respectively. Afterreceiving the conditional mobility command, UE may evaluate a mobilityexecution condition. If at least one target cell satisfies the mobilityexecution condition, the UE may initiate to access to the correspondingtarget cell using the target cell configuration for the correspondingtarget cell. For a conditional mobility, more than one target cell canbe prepared for the mobility. In case of preparation of multiple targetcells for a conditional mobility, a UE may receive a conditionalmobility command including multiple target cell configurationscorresponding to the prepared target cells.

FIG. 10 shows an example of a conditional mobility procedure to whichtechnical features of the present disclosure can be applied. The stepsillustrated in FIG. 10 can also be applied to a conditional handoverprocedure, conditional SN addition procedure and/or conditional SNchange procedure.

Referring to FIG. 10 , in step S1001, the source cell may transmitmeasurement control message to the UE. The source cell may configure theUE measurement procedures according to the roaming and accessrestriction information and, for example, the available multiplefrequency band information through the measurement control message.Measurement control information provided by the source cell through themeasurement control message may assist the function controlling the UE'sconnection mobility. For example, the measurement control message maycomprise measurement configuration and/or report configuration.

In step S1003, the UE may transmit a measurement report message to thesource cell. The measurement report message may comprise a result ofmeasurement on neighbor cell(s) around the UE which can be detected bythe UE. The UE may generate the measurement report message according toa measurement configuration and/or measurement control information inthe measurement control message received in step S1001.

In step S1005, the source cell may make a mobility decision based on themeasurement report. For example, the source cell may make a mobilitydecision and determine candidate target cells (e.g., target cell 1 andtarget cell 2) for mobility among neighbor cells around the UE based ona result of measurement (e.g., signal quality, reference signal receivedpower (RSRP), reference signal received quality (RSRP)) on the neighborcells.

In step S1007, the source cell may transmit mobility request messages tothe target cell 1 and the target cell 2 which are determined in stepS1005. That is, the source cell may perform mobility preparation withthe target cell 1 and the target cell 2. The mobility request messagemay comprise necessary information to prepare the mobility at the targetside (e.g., target cell 1 and target cell 2).

In step S1009, each of the target cell 1 and the target cell 2 mayperform an admission control based on information included in themobility request message. The target cell may configure and reserve therequired resources (e.g., C-RNTI and/or RACH preamble). TheAS-configuration to be used in the target cell can either be specifiedindependently (i.e. an “establishment”) or as a delta compared to theAS-configuration used in the source cell (i.e. a “reconfiguration”).

In step S1011, the target cell and the target cell 2 may transmit amobility request acknowledge (ACK) message to the source cell. Themobility request ACK message may comprise information on resourcesreserved and prepared for a mobility. For example, the mobility requestACK message may comprise a transparent container to be sent to the UE asan RRC message to perform the mobility. The container may include a newC-RNTI, target gNB security algorithm identifiers for the selectedsecurity algorithms, a dedicated RACH preamble, and/or possibly someother parameters i.e. access parameters, SIBs. If RACH-less mobility isconfigured, the container may include timing adjustment indication andoptionally a preallocated uplink grant. The mobility request ACK messagemay also include RNL/TNL information for forwarding tunnels, ifnecessary. As soon as the source cell receives the mobility request ACKmessage, or as soon as the transmission of the conditional mobilitycommand is initiated in the downlink, data forwarding may be initiated.

In step S1013, the source cell may transmit a conditionalreconfiguration to the UE. The conditional reconfiguration may be alsoreferred to as (or, may comprise) conditional handover (CHO)configuration and/or a conditional mobility command (e.g., CHO command).The conditional configuration may comprise a conditional reconfigurationfor each of the candidate target cells (e.g., target cell 1, target cell2). For example, the conditional reconfiguration may comprise aconditional reconfiguration for the target cell 1, and a conditionalreconfiguration for the target cell 2. The conditional reconfigurationfor the target cell 1 may comprise a mobility condition for the targetcell 1, and a target cell configuration for the target cell 1. Thetarget cell configuration for the target cell 1 may comprise RRCreconfiguration parameters associated with a mobility to the target cell1, including information on resources reserved for the mobility to thetarget cell 1. Similarly, the conditional reconfiguration for the targetcell 2 may comprise a mobility condition for the target cell 2, and atarget cell configuration for the target cell 2. The target cellconfiguration for the target cell 2 may comprise RRC reconfigurationparameters associated with a mobility to the target cell 2, includinginformation on resources reserved for the mobility to the target cell 2.

The mobility condition may inform at least one measurement ID. Forexample, the mobility condition may inform at most 2 measurement IDs. Ifa mobility condition of a target cell informs a measurement ID which isrelated to a measurement object A and a report configuration B,evaluating the mobility condition may comprise determining whether ameasurement result on the measurement object A satisfies a reportcondition in the report configuration B. If the measurement result onthe measurement object A satisfies the report condition in the reportconfiguration B according to the evaluation of the mobility condition,the UE may determine that the mobility condition of the target cell issatisfied (or, the target cell/measurement result for the target cellsatisfies the mobility condition of the target cell), and perform amobility to the target cell.

In step S1015, the UE may perform an evaluation of the mobilitycondition for the candidate target cells (e.g., target cell 1, targetcell 2) and select a target cell for a mobility among the candidatetarget cells. For example, the UE may perform measurements on thecandidate target cells, and determine whether a candidate target cellsatisfies a mobility condition for the candidate target cell among thecandidate target cells based on a result of the measurements on thecandidate target cells. If the UE identifies that the target cell 1satisfies a mobility condition for the target cell 1, the UE may selectthe target cell 1 as a target cell for the mobility.

In step S1017, the UE may perform a random access to the selected targetcell (e.g., target cell 1). For example, the UE may transmit a randomaccess preamble to the target cell 1, and receive a random accessresponse comprising an uplink grant from the target cell 1. If RACH-lessmobility is configured, the step S1017 may be omitted, and the uplinkgrant may be provided in step S1013.

In step S1019, the UE may transmit a mobility complete message to thetarget cell 1. When the UE has successfully accessed the target cell 1(or, received uplink grant when RACH-less mobility is configured), theUE may transmit a mobility complete message comprising a C-RNTI toconfirm the mobility, along with uplink buffer status report, wheneverpossible, to the target cell 1 to indicate that the mobility procedureis completed for the UE. The target cell 1 may verify the C-RNTItransmitted in the mobility complete message.

In step S1021, the target cell 1 may transmit a sequence number (SN)status request message to the source cell. The target cell 1 may requestthe source cell to inform the target cell 1 of a SN of a packet thetarget cell 1 has to transmit after the mobility, via the SN statusrequest message.

In step S1023, the source cell may transmit a conditional mobilitycancellation message to the target cell 2 which is not selected as atarget cell for a mobility among the candidate target cells. Afterreceiving the conditional mobility cancellation message, the target cell2 may release resources that are reserved in case of a mobility.

In step S1025, the target cell 2 may transmit a conditional mobilitycancellation confirmation message to the source cell, as a response forthe conditional mobility cancellation message. The conditional mobilitycancellation confirmation message may inform that the target cell 2 hasreleased resources reserved in case of a mobility.

In step S1027, the source cell may transmit a SN status transfer messageto the target cell 1, as a response for the SN status request message.The SN status transfer message may inform the target cell 1 of a SN of apacket the target cell 1 has to transmit after the mobility.

In step S1029, the source cell may perform a data forwarding to thetarget cell 1. For example, the source cell may forward data receivedfrom a core network to the target cell 1 so that the target cell 1 cannow transmit the data to the UE.

In the disclosure, various timer may be used. Such various timers maycomprise T310 timer and T312 timer.

UE may start T310 timer upon detecting physical layer problems for aPCell. For example, the UE may start T310 timer upon receiving N310consecutive out-of-sync indications from lower layers. UE may stop theT310 timer upon receiving N311 consecutive in-sync indications fromlower layers for the PCell, upon triggering the handover procedureand/or upon initiating the connection re-establishment procedure. At theexpiry of the T310 timer, the UE may declare a radio link failure (RLF).The T310 timer may be referred to as RLF timer.

UE may start T312 timer upon triggering a measurement report for ameasurement identity for which T312 has been configured, while T310 isrunning. The measurement report may be triggered when/if a reportcondition in a report configuration is satisfied. The UE may stop theT312 timer upon receiving N311 consecutive in-sync indications fromlower layers, upon triggering the handover procedure, upon initiatingthe connection re-establishment procedure, and/or upon the expiry of theT310 timer. At the expiry of the T312 timer, the UE may declare the RLF.The T312 timer may be referred to as early RLF timer.

According to the various embodiments, UE shall not stop T310 and shallnot start T304 when the UE receives a configuration of a CHO candidate(i.e., conditional reconfiguration and/or a conditional mobilitycommand).

According to various embodiments, the timer T310 may be stopped andtimer T304-like may be started when the UE begins an execution of aconditional mobility for a target cell.

According to various embodiments, at RLF, the UE may perform cellselection and if the selected cell is a CHO candidate, then the UE mayattempt CHO execution; otherwise, re-establishment may be performed.

According to various embodiments, if/when accessing a CHO candidate cellfails (i.e., at T304-like expiry), the UE may perform cell selection andif the selected cell is a CHO candidate, then the UE may attempt CHOexecution; otherwise, re-establishment may be performed.

FIG. 11 shows an example of a case in which a measurement report istriggered after an entry condition for CHO is met.

Referring to FIG. 11 , UE may starts T312 timer if a certain measurementreporting is triggered while T310 timer is running. Consider a case acandidate cell for conditional handover has satisfied an entry conditionof CHO execution condition (but TTT has not yet expired). For instance,the UE in FIG. 11 has been configured with neighbour cell A for CHO andthe entry condition of CHO execution condition is fulfilled for cell A.Before TTT for CHO expires, the measurement report may be triggered byanother neighbour cell B while T310 timer is running. Since themeasurement report is triggered, the UE may start T312 timer in thiscase. If T312 timer expires before TTT for CHO expires, UE may declareRLF, and may be deprived of the chance of CHO even though there is ahigh possibility of CHO success (i.e., even though the entry conditionfor CHO is met).

FIG. 12 shows an example of a case in which a measurement report istriggered before an entry condition for CHO is met.

Referring to FIG. 12 , upon detecting that a measurement report istriggered for cell B, UE may start T312 timer. While the T312 timer isrunning, an entry condition for CHO may be met for cell A. If T312 timerexpires before TTT for CHO expires, UE may declare RLF, and may bedeprived of the chance of CHO even though there is a high possibility ofCHO success (i.e., even though the entry condition for CHO is met).

In scenarios such as FIG. 11 , and FIG. 12 , if the UE doesn't supportT312 based function, the UE would complete successfully the CHO withoutRLF declaration. However, the UE in FIG. 11 cannot complete the CHO justbecause the UE supports an enhanced mechanism based on T312. The T312based mechanism should not degrade CHO performance. Therefore, variousembodiments of the present disclosure provide solutions to handling thescenarios. The solutions may comprise i) stopping the early RLF timerand/or T312 timer if/when an entry condition of a mobility executioncondition for a conditional mobility is satisfied while the T312 timeris running; and/or ii) refraining from starting the early RLF timerand/or T312 timer after an entry condition of a mobility executioncondition for a conditional mobility is satisfied.

FIG. 13 shows an example of a method for handling a timer related to RLFaccording to an embodiment of the present disclosure. Steps illustratedin FIG. 13 may be performed by a wireless device and/or a UE.

Referring to FIG. 13 , in step S1301, the wireless device may receive aconditional mobility command comprising a mobility execution conditionfor a target cell.

In step S1303, the wireless device may detect that an entering conditionof the mobility execution condition is satisfied while a timer isrunning. The timer may be a timer whose expiry causes the wirelessdevice to detect an RLF.

In step S1305, the wireless device may stop the timer based on detectingthat the entering condition of the mobility execution condition issatisfied.

In step S1307, the wireless device may perform a mobility to the targetcell based on that the entering condition is satisfied for at least aTTT related to the mobility execution condition.

According to various embodiments, the wireless device may start thetimer upon receiving a predetermined number (e.g., N310) of consecutiveout-of-sync indications from lower layers than a radio resource control(RRC) layer. In this case, the timer may be T310 timer and/or RLF timer.

According to various embodiments, the wireless device may start an RLFtimer upon receiving a predetermined number of consecutive out-of-syncindications from lower layers than a radio resource control (RRC) layer,wherein an RLF is detected upon an expiry of the RLF timer. The wirelessdevice may start the timer upon detecting that a measurement reportingis triggered while the RLF timer is running. In this case, the timer maybe an early RLF timer and/or T312.

According to various embodiments, a running duration of the timer may besmaller than that of the RLF timer.

According to various embodiments, the RLF timer may stop as the timerstops.

According to various embodiments, the timer may be started based on thatan entering condition of a mobility execution condition for aconditional mobility is not satisfied for any target cell. That is, thetimer may not be started after an entering condition of a mobilityexecution condition for a conditional mobility is satisfied for anytarget cell.

According to various embodiments, the wireless device may stop the timerupon detecting that the entering condition of the mobility executioncondition is satisfied.

According to various embodiments, the wireless device may stop the timerupon detecting that the entering condition of the mobility executioncondition is satisfied for at least a period. The period may comprise atleast one of the TTT, or a period that is set to smaller than the TTT.

According to various embodiments, the wireless device may stop the timerupon determining that the mobility to the target cell is successfullycompleted. That is, the wireless device may stop the timer upondetermining that accessing to the target cell according to the mobilityis successfully completed.

According to various embodiments, the entering condition may comprise atleast one of: an event A3 entering condition that a signal quality forthe target cell is better than that for a source cell more than or equalto the offset value; an event A5 entering condition that a signalquality for the target cell is better than a first threshold and asignal quality for the source cell is lower than a second threshold; acondition that a signal quality for the target cell is better than thatfor a source cell; or a condition that a signal quality for the targetcell is better than a threshold.

According to various embodiments, the timer may comprise at least one ofa T312 timer or a T310 timer.

According to various embodiments, the wireless device may receive amobility command including an entry condition for mobility execution.The wireless device may detect radio link problem. The wireless devicemay start a timer upon triggering a measurement reporting based on thatthe entry condition for mobility execution is not fulfilled. Thewireless device may stop the timer based on that the entry condition formobility execution condition is fulfilled.

FIG. 14 shows another example of a method for handling a timer relatedto RLF according to an embodiment of the present disclosure. Stepsillustrated in FIG. 14 may be performed by a wireless device and/or aUE.

Referring to FIG. 14 , in step S1401, the wireless device may receive,from a network, a conditional mobility command related to a candidatecell comprising a mobility execution condition. The conditional mobilitycommand may include an entry condition and a candidate cellconfiguration/target cell configuration. The mobility may includeserving cell change, addition and/or deletion. The serving cell mayinclude PCell, PSCell and/or SCell. UE may perform the mobility if theentry condition is fulfilled for the candidate cell during a certainperiod of time (e.g., TTT).

In step S1403, the UE may detect a radio link problem. The UE may starta timer A (e.g., T310 timer and/or RLF timer) when/if a certaincondition related to the radio link problem is met. For example, the UEmay start the timer A upon receiving N310 consecutive out-of-syncindications from lower layers. If the timer A expires, the UE maydeclare RLF. UE may stop the timer A when/if the radio link problem isresolved.

In step S1405, the UE may determine that a report condition related toan event for which an early RLF timer is configured is satisfied. Thatis, the UE may determine that a measurement reporting is triggered.

In step S1407, the UE may start a timer B (e.g., T312 and/or early RLFtimer). If the entry condition of a mobility execution condition is notfulfilled for the candidate cell, UE may start the timer B. The timer Bmay be for early RLF declaration. UE may declare the radio link failurewhen/if the timer B expires. Upon RLF declaration, UE may initiate RRCre-establishment procedure to recover the RRC connection. The timer Bmay be set to a smaller time value than timer A. UE may stop the timer Bwhen the UE receives a mobility command from a network, and/or when theradio link problem is resolved. UE may not start the timer B for earlyRLF declaration when/if the entry condition of a mobility executioncondition for conditional mobility is fulfilled for the candidate cell.

In step S1409, the UE may stop the timer B when/if an entry condition ofthe mobility execution condition for conditional mobility is fulfilledfor the candidate cell while the timer B is running. Desirably, UE maystop the timer B if the entry condition of the mobility executioncondition for the conditional mobility is fulfilled for the candidatecell during a certain period of time. The certain period of time can betime to trigger. Or for the certain period of time, smaller time valuecan be set than the timer to trigger. Alternatively, the UE may stop thetimer B when/if the conditional mobility is successfully completed. Thatis, if UE successfully accesses to the candidate cell, UE may stop thetimer B. The same stop condition can be applied to the timer A. That is,if above condition is met, UE may stop timer A. The entry condition canbe set to ‘neighbour cell (candidate cell) quality becomes better thanserving cell quality’ and/or ‘neighbour cell (candidate cell) qualitybecomes better than a threshold’.

Various embodiments of the present disclosure can also be applied toconditional PCell/PSCell change as the followings 1)-4):

1) UE can start T312 for PCell/PSCell if/when the entry condition of amobility condition for conditional PCell/PSCell change is not fulfilled.

2) UE can start T312 for PCell/PSCell if/when all configured entryconditions of a mobility condition for conditional PCell/PSCell changeare not fulfilled. That is, while T310 is running, even if a measurementreporting is triggered, for which the T312 is set to use, and if theentry condition for conditional PCell change is fulfilled, UE may notstart T312. While T310 is running, if a measurement reporting istriggered, for which the T312 is set to use, and if the entry conditionfor conditional PCell change is not fulfilled, UE may start T312.

3) UE may stop T312 for PCell/PSCell when/if the entry condition of amobility condition for conditional PCell/PSCell change is fulfilled andT312 is running.

4) UE may stop T312 for PCell/PSCell when/if at least one of configuredentry condition of a mobility condition for conditional PCell/PSCellchange is fulfilled and T312 is running.

FIG. 15 shows an example of a signal flow for handling a timer relatedto RLF according to an embodiment of the present disclosure.

Referring to FIG. 15 , in step S1501, a base station (BS) may transmit,to a wireless device, a conditional mobility command comprising amobility execution condition for a target cell.

In step S1503, the wireless device may detect that an entering conditionof the mobility execution condition is satisfied while a timer isrunning. The timer may be a timer whose expiry causes the wirelessdevice to detect an RLF.

In step S1505, the wireless device may stop the timer based on detectingthat the entering condition of the mobility execution condition issatisfied.

In step S1507, the wireless device may perform a mobility to the targetcell based on that the entering condition is satisfied at least for aTTT related to the mobility execution condition.

The BS in FIG. 15 may be an example of a second device 220 in FIG. 2 ,and therefore, steps of the BS as illustrated in FIG. 15 may beimplemented by the second device 220. For example, the processor 221 maybe configured to control the transceiver 223 to transmit, to a wirelessdevice, a conditional mobility command comprising a mobility executioncondition for a target cell. The wireless device may be configured todetect that an entering condition of the mobility execution condition issatisfied while a timer is running. The timer may be a timer whoseexpiry causes the wireless device to detect an RLF. The wireless devicemay be configured to stop the timer based on detecting that the enteringcondition of the mobility execution condition is satisfied. The wirelessdevice may be configured to perform a mobility to the target cell basedon that the entering condition is satisfied at least for a TTT relatedto the mobility execution condition.

FIG. 16 shows an example of a T312 timer handling in a mobilityaccording to an embodiment of the present disclosure.

Referring to FIG. 16 , UE may receive a conditional mobility commandcomprising a mobility execution condition. The UE may start T312 timerupon detecting that a measurement reporting is triggered for Cell B. TheUE may stop the T312 timer and start TTT timer when/if the entrycondition of the mobility execution condition for conditional mobilityis fulfilled for Cell A. If the entry condition of the mobilityexecution condition for conditional mobility is fulfilled for at leastthe TTT, the UE may execute the conditional mobility.

FIG. 17 shows a UE to implement an embodiment of the present disclosure.The present disclosure described above for UE side may be applied tothis embodiment. The UE in FIG. 17 may be an example of first device 217as illustrated in FIG. 2 .

A UE includes a processor 1710 (i.e., processor 211), a power managementmodule 1711, a battery 1712, a display 1713, a keypad 1714, a subscriberidentification module (SIM) card 1715, a memory 1720 (i.e., memory 212),a transceiver 1730 (i.e., transceiver 213), one or more antennas 1731, aspeaker 1740, and a microphone 1741.

The processor 1710 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 1710. Theprocessor 1710 may include application-specific integrated circuit(ASIC), other chipset, logic circuit and/or data processing device. Theprocessor 1710 may be an application processor (AP). The processor 1710may include at least one of a digital signal processor (DSP), a centralprocessing unit (CPU), a graphics processing unit (GPU), a modem(modulator and demodulator). An example of the processor 1710 may befound in SNAPDRAGON™ series of processors made by Qualcomm®, EXYNOS™series of processors made by Samsung®, A series of processors made byApple®, HELIO™ series of processors made by MediaTek®, ATOM™ series ofprocessors made by Intel® or a corresponding next generation processor.

The processor 1710 may be configured to, or configured to control thetransceiver 1730 to implement steps performed by the UE and/or thewireless device throughout the disclosure.

The power management module 1711 manages power for the processor 1710and/or the transceiver 1730. The battery 1712 supplies power to thepower management module 1711. The display 1713 outputs results processedby the processor 1710. The keypad 1714 receives inputs to be used by theprocessor 1710. The keypad 1714 may be shown on the display 1713. TheSIM card 1715 is an integrated circuit that is intended to securelystore the international mobile subscriber identity (IMSI) number and itsrelated key, which are used to identify and authenticate subscribers onmobile telephony devices (such as mobile phones and computers). It isalso possible to store contact information on many SIM cards.

The memory 1720 is operatively coupled with the processor 1710 andstores a variety of information to operate the processor 1710. Thememory 1720 may include read-only memory (ROM), random access memory(RAM), flash memory, memory card, storage medium and/or other storagedevice. When the embodiments are implemented in software, the techniquesdescribed herein can be implemented with modules (e.g., procedures,functions, and so on) that perform the functions described herein. Themodules can be stored in the memory 1720 and executed by the processor1710. The memory 1720 can be implemented within the processor 1710 orexternal to the processor 1710 in which case those can becommunicatively coupled to the processor 1710 via various means as isknown in the art.

The transceiver 1730 is operatively coupled with the processor 1710, andtransmits and/or receives a radio signal. The transceiver 1730 includesa transmitter and a receiver. The transceiver 1730 may include basebandcircuitry to process radio frequency signals. The transceiver 1730controls the one or more antennas 1731 to transmit and/or receive aradio signal.

The speaker 1740 outputs sound-related results processed by theprocessor 1710. The microphone 1741 receives sound-related inputs to beused by the processor 1710.

According to various embodiments, the processor 1710 may be configuredto, or configured to control the transceiver 1730 to implement stepsperformed by the UE and/or the wireless device throughout thedisclosure. For example, the processor 1710 may be configured to controlthe transceiver to receive a conditional mobility command comprising amobility execution condition for a target cell. The processor 1710 maybe configured to detect that an entering condition of the mobilityexecution condition is satisfied while a timer is running. A radio linkfailure (RLF) is detected upon an expiry of the timer. The processor1710 may be configured to stop the timer based on detecting that theentering condition of the mobility execution condition is satisfied. Theprocessor 1710 may be configured to perform a mobility to the targetcell based on that the entering condition is satisfied for at least atime to trigger (TTT) related to the mobility execution condition.

According to various embodiments, the conditional mobility command maycomprise a target cell configuration for the target cell. The processor1710 may be configured to perform the mobility to the target cell byapplying the target cell configuration for the target cell.

According to various embodiments, the processor 1710 may be configuredto start the timer upon receiving a predetermined number of consecutiveout-of-sync indications from lower layers than a radio resource control(RRC) layer.

According to various embodiments, the processor 1710 may be configuredto start an RLF timer upon receiving a predetermined number ofconsecutive out-of-sync indications from lower layers than a radioresource control (RRC) layer, wherein an RLF is detected upon an expiryof the RLF timer. The processor 1710 may be configured to start thetimer upon detecting that a measurement reporting is triggered while theRLF timer is running.

According to various embodiments, a running duration of the timer may besmaller than that of the RLF timer.

According to various embodiments, the RLF timer may stop as the timerstops.

According to various embodiments, the timer may be started based on thatan entering condition of a mobility execution condition for aconditional mobility is not satisfied for any target cell.

According to various embodiments, the processor 1710 may be configuredto stop the timer upon detecting that the entering condition of themobility execution condition is satisfied.

According to various embodiments, the processor 1710 may be configuredto stop the timer upon detecting that the entering condition of themobility execution condition is satisfied for at least a period. Theperiod may comprise at least one of the TTT, or a period that is set tosmaller than the TTT.

According to various embodiments, the processor 1710 may be configuredto stop the timer upon determining that the mobility to the target cellis successfully completed.

According to various embodiments, the entering condition may comprise atleast one of: an event A3 entering condition that a signal quality forthe target cell is better than that for a source cell more than or equalto the offset value; an event A5 entering condition that a signalquality for the target cell is better than a first threshold and asignal quality for the source cell is lower than a second threshold; acondition that a signal quality for the target cell is better than thatfor a source cell; or a condition that a signal quality for the targetcell is better than a threshold.

According to various embodiments, the timer may comprise at least one ofa T312 timer or a T310 timer.

FIG. 18 shows another example of a wireless communication system towhich the technical features of the present disclosure can be applied.

Referring to FIG. 18 , the wireless communication system may include afirst device 1810 (i.e., first device 210) and a second device 1820(i.e., second device 220).

The first device 1810 may include at least one transceiver, such as atransceiver 1811, and at least one processing chip, such as a processingchip 1812. The processing chip 1812 may include at least one processor,such a processor 1813, and at least one memory, such as a memory 1814.The memory may be operably connectable to the processor 1813. The memory1814 may store various types of information and/or instructions. Thememory 1814 may store a software code 1815 which implements instructionsthat, when executed by the processor 1813, perform operations of thefirst device 910 described throughout the disclosure. For example, thesoftware code 1815 may implement instructions that, when executed by theprocessor 1813, perform the functions, procedures, and/or methods of thefirst device 1810 described throughout the disclosure. For example, thesoftware code 1815 may control the processor 1813 to perform one or moreprotocols. For example, the software code 1815 may control the processor1813 to perform one or more layers of the radio interface protocol.

The second device 1820 may include at least one transceiver, such as atransceiver 1821, and at least one processing chip, such as a processingchip 1822. The processing chip 1822 may include at least one processor,such a processor 1823, and at least one memory, such as a memory 1824.The memory may be operably connectable to the processor 1823. The memory1824 may store various types of information and/or instructions. Thememory 1824 may store a software code 1825 which implements instructionsthat, when executed by the processor 1823, perform operations of thesecond device 1820 described throughout the disclosure. For example, thesoftware code 1825 may implement instructions that, when executed by theprocessor 1823, perform the functions, procedures, and/or methods of thesecond device 1820 described throughout the disclosure. For example, thesoftware code 1825 may control the processor 1823 to perform one or moreprotocols. For example, the software code 1825 may control the processor1823 to perform one or more layers of the radio interface protocol.

According to various embodiments, the first device 1810 as illustratedin FIG. 18 may comprise a wireless device. The wireless device maycomprise a transceiver 1811, a processing chip 1812. The processing chip1812 may comprise a processor 1813, and a memory 1814. The memory 1814may be operably connectable to the processor 1813. The memory 1814 maystore various types of information and/or instructions. The memory 1814may store a software code 1815 which implements instructions that, whenexecuted by the processor 1813, perform operations comprising: receivinga conditional mobility command comprising a mobility execution conditionfor a target cell; detecting that an entering condition of the mobilityexecution condition is satisfied while a timer is running, wherein aradio link failure (RLF) is detected upon an expiry of the timer;stopping the timer based on detecting that the entering condition of themobility execution condition is satisfied; and performing a mobility tothe target cell based on that the entering condition is satisfied for atleast a time to trigger (TTT) related to the mobility executioncondition.

According to various embodiments, a computer-readable medium havingrecorded thereon a program for performing each step of a method on acomputer is provided. The method comprises: receiving a conditionalmobility command comprising a mobility execution condition for a targetcell; detecting that an entering condition of the mobility executioncondition is satisfied while a timer is running, wherein a radio linkfailure (RLF) is detected upon an expiry of the timer; stopping thetimer based on detecting that the entering condition of the mobilityexecution condition is satisfied; and performing a mobility to thetarget cell based on that the entering condition is satisfied for atleast a time to trigger (TTT) related to the mobility executioncondition.

The present disclosure may be applied to various future technologies,such as AI, robots, autonomous-driving/self-driving vehicles, and/orextended reality (XR).

<AI>

AI refers to artificial intelligence and/or the field of studyingmethodology for making it. Machine learning is a field of studyingmethodologies that define and solve various problems dealt with in AI.Machine learning may be defined as an algorithm that enhances theperformance of a task through a steady experience with any task.

An artificial neural network (ANN) is a model used in machine learning.It can mean a whole model of problem-solving ability, consisting ofartificial neurons (nodes) that form a network of synapses. An ANN canbe defined by a connection pattern between neurons in different layers,a learning process for updating model parameters, and/or an activationfunction for generating an output value. An ANN may include an inputlayer, an output layer, and optionally one or more hidden layers. Eachlayer may contain one or more neurons, and an ANN may include a synapsethat links neurons to neurons. In an ANN, each neuron can output asummation of the activation function for input signals, weights, anddeflections input through the synapse. Model parameters are parametersdetermined through learning, including deflection of neurons and/orweights of synaptic connections. The hyper-parameter means a parameterto be set in the machine learning algorithm before learning, andincludes a learning rate, a repetition number, a mini batch size, aninitialization function, etc. The objective of the ANN learning can beseen as determining the model parameters that minimize the lossfunction. The loss function can be used as an index to determine optimalmodel parameters in learning process of ANN.

Machine learning can be divided into supervised learning, unsupervisedlearning, and reinforcement learning, depending on the learning method.Supervised learning is a method of learning ANN with labels given tolearning data. Labels are the answers (or result values) that ANN mustinfer when learning data is input to ANN. Unsupervised learning can meana method of learning ANN without labels given to learning data.Reinforcement learning can mean a learning method in which an agentdefined in an environment learns to select a behavior and/or sequence ofactions that maximizes cumulative compensation in each state.

Machine learning, which is implemented as a deep neural network (DNN)that includes multiple hidden layers among ANN, is also called deeplearning. Deep learning is part of machine learning. In the following,machine learning is used to mean deep learning.

FIG. 19 shows an example of an AI device to which the technical featuresof the present disclosure can be applied.

The AI device 1900 may be implemented as a stationary device or a mobiledevice, such as a TV, a projector, a mobile phone, a smartphone, adesktop computer, a notebook, a digital broadcasting terminal, a PDA, aPMP, a navigation device, a tablet PC, a wearable device, a set-top box(STB), a digital multimedia broadcasting (DMB) receiver, a radio, awashing machine, a refrigerator, a digital signage, a robot, a vehicle,etc.

Referring to FIG. 19 , the AI device 1900 may include a communicationpart 1910, an input part 1920, a learning processor 1930, a sensing part1940, an output part 1950, a memory 1960, and a processor 1970.

The communication part 1910 can transmit and/or receive data to and/orfrom external devices such as the AI devices and the AI server usingwire and/or wireless communication technology. For example, thecommunication part 1910 can transmit and/or receive sensor information,a user input, a learning model, and a control signal with externaldevices. The communication technology used by the communication part1910 may include a global system for mobile communication (GSM), a codedivision multiple access (CDMA), an LTE/LTE-A, a 5G, a WLAN, a Wi-Fi,Bluetooth™, radio frequency identification (RFID), infrared dataassociation (IrDA), ZigBee, and/or near field communication (NFC).

The input part 1920 can acquire various kinds of data. The input part1920 may include a camera for inputting a video signal, a microphone forreceiving an audio signal, and a user input part for receivinginformation from a user. A camera and/or a microphone may be treated asa sensor, and a signal obtained from a camera and/or a microphone may bereferred to as sensing data and/or sensor information. The input part1920 can acquire input data to be used when acquiring an output usinglearning data and a learning model for model learning. The input part1920 may obtain raw input data, in which case the processor 1970 or thelearning processor 1930 may extract input features by preprocessing theinput data.

The learning processor 1930 may learn a model composed of an ANN usinglearning data. The learned ANN can be referred to as a learning model.The learning model can be used to infer result values for new input datarather than learning data, and the inferred values can be used as abasis for determining which actions to perform. The learning processor1930 may perform AI processing together with the learning processor ofthe AI server. The learning processor 1930 may include a memoryintegrated and/or implemented in the AI device 1900. Alternatively, thelearning processor 1930 may be implemented using the memory 1960, anexternal memory directly coupled to the AI device 1900, and/or a memorymaintained in an external device.

The sensing part 1940 may acquire at least one of internal informationof the AI device 1900, environment information of the AI device 1900,and/or the user information using various sensors. The sensors includedin the sensing part 1940 may include a proximity sensor, an illuminancesensor, an acceleration sensor, a magnetic sensor, a gyro sensor, aninertial sensor, an RGB sensor, an IR sensor, a fingerprint recognitionsensor, an ultrasonic sensor, an optical sensor, a microphone, a lightdetection and ranging (LIDAR), and/or a radar.

The output part 1950 may generate an output related to visual, auditory,tactile, etc. The output part 1950 may include a display unit foroutputting visual information, a speaker for outputting auditoryinformation, and/or a haptic module for outputting tactile information.

The memory 1960 may store data that supports various functions of the AIdevice 1900. For example, the memory 1960 may store input data acquiredby the input part 1920, learning data, a learning model, a learninghistory, etc.

The processor 1970 may determine at least one executable operation ofthe AI device 1900 based on information determined and/or generatedusing a data analysis algorithm and/or a machine learning algorithm. Theprocessor 1970 may then control the components of the AI device 1900 toperform the determined operation. The processor 1970 may request,retrieve, receive, and/or utilize data in the learning processor 1930and/or the memory 1960, and may control the components of the AI device1900 to execute the predicted operation and/or the operation determinedto be desirable among the at least one executable operation. Theprocessor 1970 may generate a control signal for controlling theexternal device, and may transmit the generated control signal to theexternal device, when the external device needs to be linked to performthe determined operation. The processor 1970 may obtain the intentioninformation for the user input and determine the user's requirementsbased on the obtained intention information. The processor 1970 may useat least one of a speech-to-text (STT) engine for converting speechinput into a text string and/or a natural language processing (NLP)engine for acquiring intention information of a natural language, toobtain the intention information corresponding to the user input. Atleast one of the STT engine and/or the NLP engine may be configured asan ANN, at least a part of which is learned according to a machinelearning algorithm. At least one of the STT engine and/or the NLP enginemay be learned by the learning processor 1930 and/or learned by thelearning processor of the AI server, and/or learned by their distributedprocessing. The processor 1970 may collect history information includingthe operation contents of the AI device 1900 and/or the user's feedbackon the operation, etc. The processor 1970 may store the collectedhistory information in the memory 1960 and/or the learning processor1930, and/or transmit to an external device such as the AI server. Thecollected history information can be used to update the learning model.The processor 1970 may control at least some of the components of AIdevice 1900 to drive an application program stored in memory 1960.Furthermore, the processor 1970 may operate two or more of thecomponents included in the AI device 1900 in combination with each otherfor driving the application program.

FIG. 20 shows an example of an AI system to which the technical featuresof the present disclosure can be applied.

Referring to FIG. 20 , in the AI system, at least one of an AI server2020, a robot 2010 a, an autonomous vehicle 2010 b, an XR device 2010 c,a smartphone 2010 d and/or a home appliance 2010 e is connected to acloud network 2000. The robot 2010 a, the autonomous vehicle 2010 b, theXR device 2010 c, the smartphone 2010 d, and/or the home appliance 2010e to which the AI technology is applied may be referred to as AI devices2010 a to 2010 e.

The cloud network 2000 may refer to a network that forms part of a cloudcomputing infrastructure and/or resides in a cloud computinginfrastructure. The cloud network 2000 may be configured using a 3Gnetwork, a 4G or LTE network, and/or a 5G network. That is, each of thedevices 2010 a to 2010 e and 2020 consisting the AI system may beconnected to each other through the cloud network 2000. In particular,each of the devices 2010 a to 2010 e and 2020 may communicate with eachother through a base station, but may directly communicate with eachother without using a base station.

The AI server 2020 may include a server for performing AI processing anda server for performing operations on big data. The AI server 2020 isconnected to at least one or more of AI devices constituting the AIsystem, i.e. the robot 2010 a, the autonomous vehicle 2010 b, the XRdevice 2010 c, the smartphone 2010 d and/or the home appliance 2010 ethrough the cloud network 2000, and may assist at least some AIprocessing of the connected AI devices 2010 a to 2010 e. The AI server2020 can learn the ANN according to the machine learning algorithm onbehalf of the AI devices 2010 a to 2010 e, and can directly store thelearning models and/or transmit them to the AI devices 2010 a to 2010 e.The AI server 2020 may receive the input data from the AI devices 2010 ato 2010 e, infer the result value with respect to the received inputdata using the learning model, generate a response and/or a controlcommand based on the inferred result value, and transmit the generateddata to the AI devices 2010 a to 2010 e. Alternatively, the AI devices2010 a to 2010 e may directly infer a result value for the input datausing a learning model, and generate a response and/or a control commandbased on the inferred result value.

Various embodiments of the AI devices 2010 a to 2010 e to which thetechnical features of the present disclosure can be applied will bedescribed. The AI devices 2010 a to 2010 e shown in FIG. 20 can be seenas specific embodiments of the AI device 1900 shown in FIG. 19 .

In the present disclosure, a CHO has been exemplary mentioned as aconditional mobility for the sake of convenience. The present disclosurecan also be applied to other forms of conditional mobility, such asconditional PSCell/SCell change without loss of generality. Furthermore,the present disclosure can be applied to normal mobility instead ofconditional mobility.

The present disclosure can have various advantageous effects.

For example, UE may not start the timer for early RLF declarationif/when an entry condition of a mobility condition for a conditionalmobility is fulfilled for a candidate cell. Also, the UE may stop thetimer for early RLF declaration if/when an entry condition of a mobilitycondition for a conditional mobility is fulfilled for the candidate cellwhile the timer is running. Therefore, the UE can complete theconditional mobility without RLF declaration, so the serviceinterruption time spent on the RRC connection recovery can be avoided.

Advantageous effects which can be obtained through specific embodimentsof the present disclosure are not limited to the advantageous effectslisted above. For example, there may be a variety of technical effectsthat a person having ordinary skill in the related art can understandand/or derive from the present disclosure. Accordingly, the specificeffects of the present disclosure are not limited to those explicitlydescribed herein, but may include various effects that may be understoodor derived from the technical features of the present disclosure.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope of the present disclosure.

Claims in the present description can be combined in a various way. Forinstance, technical features in method claims of the present descriptioncan be combined to be implemented or performed in an apparatus, andtechnical features in apparatus claims can be combined to be implementedor performed in a method. Further, technical features in method claim(s)and apparatus claim(s) can be combined to be implemented or performed inan apparatus. Further, technical features in method claim(s) andapparatus claim(s) can be combined to be implemented or performed in amethod. Other implementations are within the scope of the followingclaims.

1. A method performed by a wireless device in a wireless communicationsystem, the method comprising: receiving a conditional mobility commandcomprising a mobility execution condition for a target cell; detectingthat an entering condition of the mobility execution condition issatisfied while a timer is running, wherein a radio link failure (RLF)is detected upon an expiry of the timer; stopping the timer based ondetecting that the entering condition of the mobility executioncondition is satisfied; and performing a mobility to the target cellbased on that the entering condition is satisfied for at least a time totrigger (TTT) related to the mobility execution condition.
 2. The methodof claim 1, wherein the conditional mobility command comprises a targetcell configuration for the target cell, and wherein the performing ofthe mobility comprises performing the mobility to the target cell byapplying the target cell configuration for the target cell.
 3. Themethod of claim 1, further comprising: starting the timer upon receivinga predetermined number of consecutive out-of-sync indications from lowerlayers than a radio resource control (RRC) layer.
 4. The method of claim1, further comprising: starting an RLF timer upon receiving apredetermined number of consecutive out-of-sync indications from lowerlayers than a radio resource control (RRC) layer, wherein an RLF isdetected upon an expiry of the RLF timer; and starting the timer upondetecting that a measurement reporting is triggered while the RLF timeris running.
 5. The method of claim 4, wherein a running duration of thetimer is smaller than that of the RLF timer.
 6. The method of claim 4,wherein the RLF timer stops as the timer stops.
 7. The method of claim1, wherein the timer is started based on that an entering condition of amobility execution condition for a conditional mobility is not satisfiedfor any target cell.
 8. The method of claim 1, wherein the stopping thetimer comprises stopping the timer upon detecting that the enteringcondition of the mobility execution condition is satisfied.
 9. Themethod of claim 1, wherein the stopping the timer comprises stopping thetimer upon detecting that the entering condition of the mobilityexecution condition is satisfied for at least a period, wherein theperiod comprises at least one of the TTT, or a period that is set tosmaller than the TTT.
 10. The method of claim 1, wherein the stoppingthe timer comprises stopping the timer upon determining that themobility to the target cell is successfully completed.
 11. The method ofclaim 1, wherein the entering condition comprises at least one of: anevent A3 entering condition that a signal quality for the target cell isbetter than that for a source cell more than or equal to the offsetvalue; an event A5 entering condition that a signal quality for thetarget cell is better than a first threshold and a signal quality forthe source cell is lower than a second threshold; a condition that asignal quality for the target cell is better than that for a sourcecell; or a condition that a signal quality for the target cell is betterthan a threshold.
 12. The method of claim 1, wherein the timer comprisesat least one of a T312 timer or a T310 timer.
 13. The method of claim 1,wherein the wireless device is in communication with at least one of auser equipment, a network, or autonomous vehicles other than thewireless device.
 14. A wireless device in a wireless communicationsystem comprising: a transceiver; a memory; and at least one processoroperatively coupled to the transceiver and the memory, and configuredto: control the transceiver to receive a conditional mobility commandcomprising a mobility execution condition for a target cell; detect thatan entering condition of the mobility execution condition is satisfiedwhile a timer is running, wherein a radio link failure (RLF) is detectedupon an expiry of the timer; stop the timer based on detecting that theentering condition of the mobility execution condition is satisfied; andperform a mobility to the target cell based on that the enteringcondition is satisfied for at least a time to trigger (TTT) related tothe mobility execution condition. 15-17. (canceled)
 18. A non-transitorycomputer-readable medium having recorded thereon a program forperforming each step of a method on a computer, the method comprising:receiving a conditional mobility command comprising a mobility executioncondition for a target cell; detecting that an entering condition of themobility execution condition is satisfied while a timer is running,wherein a radio link failure (RLF) is detected upon an expiry of thetimer; stopping the timer based on detecting that the entering conditionof the mobility execution condition is satisfied; and performing amobility to the target cell based on that the entering condition issatisfied for at least a time to trigger (TTT) related to the mobilityexecution condition.